It is well known in the prior art to produce an air cell cushioning dunnage product utilizing flexible plastic sheet material and embossing one of the sheets, and applying a laminating or cover sheet thereto, for sealing formation of the air cells, with the product being utilized in cushioning applications. U.S. Pat. No. 3,416,984 dated Dec. 17, 1968 and entitled Method and Apparatus For Making Cellular Material From Thermoplastic Sheets is an example of such prior art.
In such patent, a heat sealable plastic sheet is heated to bring its outer surface to a temperature in the vicinity of the fusion or melting temperature thereof, and is embossed on a vacuum drum, with the other surface of the embossed sheet being maintained at about the fusion temperature of the plastic, and then the laminating sheet is applied to the embossed sheet while the latter is on the embossing drum, with the surface of the laminating sheet which is to contact the embossed sheet being at a temperature above the fusion temperature thereof, so that when the laminating sheet is applied to the embossed sheet, the contacting surfaces will equalize at a temperature at least equal to the fusion temperature, thus adhering or sealing the films together.
U.S. Pat. No. 3,392,081 discloses a multi-laminate cushioning product formed of a plurality of layers of material including a high density plastic layer and a lower density low melting point plastic layer, with the high density plastic layer being selected from the group consisting of polyvinylidene chloride and polyethylene, and the low density plastic layer being selected from the group consisting of polyethylene, polypropylene and polyethylene terephthalate.
Moreover, there are considerable other patents in the air cell cushioning dunnage field, such as for instance Australian Pat. No. 160,551 published Oct. 29, 1953, and U.S. Pat. Nos. 3,018,015; 3,142,599; 3,231,454; 3,285,793; 3,349,990; 3,577,305; 3,389,534; 3,523.055; 3,575,781; 3,616,155; 3,785,899; 3,817,803; 3,837,990; 3,837,991; 3,868,056; 4,076,872 and 4,096,306.
The prior art air cell products do not possess the strength of the product of the present invention, and the prior art methods and apparatus are not generally of the type which can be readily and conveniently interrupted in operation and then restarted, without having considerable undesirable effects upon the resultant product, on the stock material utilized to produce the product, and/or on the mechanism or apparatus per se.